Zone isolation adapter for packers



Dec. 28, 1965 L. PYLE 3,225,832

ZONE ISOLATION ADAPTER FOR PACKERS Filed May 22, 1965 5 Sheets-Sheet 1 v Fig.2 F/g./ 78

\ D I l i 50. I0 /6 I g 1 /2 54 -o o; i 0 0' eon P /e /0 f /0 L y T? o INVENTOR.

' 9 46 88 40 BY 42-; 46 4442 WW 3% Dec. 28, 1965 L. PYLE ZONE ISOLATION ADAPTER FOR PACKERS 5 Sheets-Sheet 2 Filed May 22, 1965 Leon Pyle 1NVENTOR.

9 BY Wily-fi Dec. 28, 1965 L. PYLE 3,

ZONE ISOLATION ADAPTER FOR PACKERS Filed May 22, 1965 5 Sheets-Sheet 5 i llllll "Em INVENTOR.

' 2 L 42 Fig. /0 BY adfluwy Em United States Patent Ofi ice 3,225,832 Patented Dec. 28, 1965 3,225,832 ZONE ISOLATION ADAPTER FOR PACKERS Leon Pyle, 1503 Leslie St., Bossier City, La. Filed May 22, 1963, Ser. No. 282,312 2 Claims. (Cl. 166-446) This invention comprises a novel and useful zone isolation adapter for packers and more particularly pertains to an adapter or attachment unit secured to or mounted upon a conventional packer of the tension packer type and cooperating therewith to effect the isolation of a formation Zone therebetween for various purposes including testing, acid-izing or fracturing.

It is frequently desirable for various purposes to effect the complete isolation or sealing-in of a selected zone in -a cased well bore in order to perform various treating or testing operations with respect to the isolated zone. Heretofore, it has frequently been a time-consuming, a laborious and a relatively expensive operation to isolate a given zone and then perform the desired operations thereat. It is therefore the primary purpose of this invention to provide a device which will facilitate and render more effective and more certain the effective isolation of a selected zone in a cased well bore.

A further object of the invention is to provide a packer adapter or attachment which is capable of being associated with a conventional tension-type packer whereby the assembled device may be effectively handled as a unit in effecting the isolating of a particular zone in a cased well bore, treating that zone and then removing the assembly from the well bore.

A further object of the invention is to provide a device in accordance with the immediately preceding object which shall include a by-pass passage means openable selectively to effect free flow of easing fluid through the device during the trips into and out of the well bore whereby to avoid the creation of turbulence in the fluid or a swabbing action resulting from passage of the device therethrough.

A still further object of the invention is to provide a zone isolating packer assembly in accordance with the preceding objects which is especially capable of and is well adapted for use inside a well casing and after the casing setting or cementing operation has been performed.

A further object of the invention is to provide a device in compliance with the preceding objects which will eliminate the necessity for mechanical connections from the surface to the device for effecting its operation and manipulation and shall rely primarily upon hydraulic means for rendering the device operative for treating or testing a formation after the device has been run into and set in the well bore.

A further and more specific object of the invention in compliance with the immediately preceding object is to provide a device in which hydraulic pressure is utilized to rupture a shear pin which retains the elements of the device in a position suitable for a trip into or out of the well bore and which, when the pin is sheared enables the hydraulic pressure to close the safety by-pass valve and condition the device for effecting a desired operation upon the isolated formation zone.

Yet another object of the invention is to provide an apparatus in accordance with the preceding objects which will enable a plurality of successive formation isolating and treating operations to 'be performed during one trip of the device in the well bore by preventing back flow from the treated or isolated zone after release of the tension packer and the slight upward movement of the device above the treated zone, thus allowing the movement of the assembly to another upper zone for treatment thereof and eliminating the necessity for making a round trip with a string of tubing each time a perforated interval of a well bore is to be tested or otherwise treated.

Still another object of the invention is to provide an apparatus in accordance with the preceding objects in which the zone isolation adapter may be applied to and operatively associated with a conventional tension packer without in any way interfering with the normal operation of the latter.

A further and more specific object of the invention is to provide a device in accordance with the preceding objects in which a two-piece telescoping mandrel is utilized as a valve means for treating the isolated zone.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully herein-after described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like par-ts throughout, and in which:

FIGURE 1 is a view in side elevation of the complete assembly of a conventional tension packer and the zone isolation adapter of this invention applied thereto, parts being broken away and the position of the invention in a cased Well being indicated in phantom;

FIGURE 2 is a view partly in elevation and partly in vertical central section, parts being broken away and showing upon an enlarged scale the construction of the zone isolation adapter of this invention with its components in the position assumed in readiness for a trip down or running into the well;

FIGURE 3 is a view similar to FIGURE 2 but with the tool components being disposed in the position which they assume in preparation for the testing or treating of an isolated formation zone;

FIGURE 4 is a view similar to FIGURE 2 but showing the position of the parts of the device in readiness for the upward trip or removal of the device from the well casing;

FIGURES 5 and 6 are detail views taken upon an enlarged scale and in horizontal section substantially upon the planes indicated by the section lines 5-5 and 66, respectively, of FIGURE 2;

FIGURE 7 is a detail view taken upon an enlarged scale in horizontal section substantially upon the plane indicated by the section line 77 of FIGURE 3;

FIGURE 8 is an enlarged detail view of the safety by-pass valve in the formation treating position of the tool as shown in FIGURE 3, and is taken in vertical section substantially upon the plane indicated by the section line 8-8 of FIGURE 7;

FIGURE 9 is a fragmentary enlarged detail view in vertical section and showing further details of the safety by-pass valve assembly, being taken substantially upon the plane indicated by the section line 99 of FIGURE 7;

FIGURE 10 is an enlarged horizontal sectional view taken substantially upon the plane indicated by the section line 1010 of FIGURE 2; and,

FIGURE 11 is an eXplOded perspective view, parts being broken away and other parts shown in section of the components of the zone isolation adapter of FIG- URE 2.

Reference is made first to FIGURE 1 wherein the numeral 10 designates generally a zone isolation packer assembly comprising the complete tool with which this invention is concerned and which is utilized to completely isolate a selected formation zone at any desired location within a cased well bore indicated generally by the numeral 12 in phantom by dot-and-dash lines. It will be appreciated that the tool is of such maximum external diameter that it may readily pass through the cased well bore during its running in and removal or upward trips. The zone isolation packer assembly consists of an upward component indicated generally by the numeral 14 and which consists of any conventional type of packer such as a tension packer and which is commonly employed to seal a well bore. Inasmuch as the precise structure and the details of structure and operation of a packer of this character are well known to those skilled in the art and in themselves form no part of the invention set forth and claimed hereinafter, a further description thereof is deemed to be unnecessary. The zone isolation packer assembly further includes as a lower component the Zone isolation adapter indicated generally by the numeral 16 and whose construction and operation in itself and in association with the tension packer 14 forms the essence of the invention set forth and claimed hereinafter.

The zone isolation packer assembly is mounted in a conventional manner upon the lower end. of a string of pipe or tubing 18 whereby the tool may be readily moved vertically in the cased well bore with precision to a selected position and may be supplied with hydraulic fluid for certain operations of portions of the Zone isolation adapter or with fluids for various formation-treating purposes of the isolated zone.

The zone isolation adapter 16 is detachably secured to the (lower end of the usual mandrel of the tension packer 14 and by means of a passage through the tension packer is placed in communication with the pipe or tubing 18. Alternatively, the mandrel of the adapter 16 may extend through and constitute the usual mandrel of the tension packer 14.

Reference is now made especially to FIGURES 2 and 11 for an understanding of the structure and the relationship of the components or elements which make-up the zone isolator adapter, FIGURE 2 showing the parts in their initial or normal position in readiness for and during the initial trip of the device into a cased well bore. It will be appreciated that the device, with the parts in the position shown in FIGURE 2, may be repeatedly moved vertically upwardly or downwardly in a well bore without diificulty.

The zone isolation adapter 16 includes a hallow mandrel of two-piece construction and which is designated generally by the numeral 20. The mandrel includes an upper section 22 which is apertured as at 24 by a multitude of perforations. This upper section may be secured to the lower end of the tension packer mandrel or alternatively may in replacement of the latter extend through the tension packer 14 and be engaged with the lower end of the pipe or tubing 18.

The mandrel further includes a lower section or sleeve 30 which is threadedly engaged with the lower end of the upper section 22 to form therewith the complete tubular mandrel. The mandrel lower section includes one or more mandrel by-pass ports 32 by means of which communication between the interior of the mandrel and the well bore is controllably established as set forth hereinafter. Below the port 32 the mandrel is externally threaded as at 34 for the reception of a safety release nut 36 engaged thereon for a purpose to be subsequently apparent.

Adjacent its lower end the mandrel lower section 30 is provided with a plurality of mandrel by-pass inlet ports 38 while the lower extremity of the mandrel is open and is externally threaded as at 40 for the reception of a retainer nut or retainer cap 42 having a diametrically reduced depending neck 44 open at its lower end. The lower end of the mandrel lower section and the retainer cap 42 constitute part of a by-pass valve assembly designated generally by the numeral 46 which contains therein a slidable, piston or sleeve type of by-pass valve indicated generally by the numeral 4. The structure and operation of this by-pass valve assembly will be set forth in detail hereinafter.

A mandrel spacer sleeve 50 embraces in spaced relation the mandrel upper section 22, having an internal annular flange or rib 52 by which it slidably embraces the mandrel section 22. It will be noted from FIGURES 2-4 and 11 that the spacer sleeve is concentric with and disposed in spaced relation to the mandrel upper sleeve 22. Adjacent its lower end the spacer sleeve is provided with perforations or ports 54- by means of which treating agents may be supplied from the interior of the mandrel and the annular space between the spacer sleeve and the mandrel upper section 22 into the isolated zone, or fluids may be withdrawn therefrom.

The open lower end of the spacer sleeve just below the lowermost of the treating perforations 54 is externally threaded as at 56 for threaded engagement with the in ternally threaded spacer sleeve cap or header assembly 58 from which depends a diametrically reduced neck or stem 60 which slidably embraces the exterior surface of the upper end of the lower mandrel section or sleeve 30. It will now be apparent that the spacer sleeve 50 is slidably journaled upon the upper and lower mandrel section or sleeves by means of the elements 52 and 58 which constitute bearings therefor, the neck 60 additionally serving as a spacer sleeve as set forth hereinafter.

Slidab ly secured upon the exterior of the lower mandrel section or sleeve 30 is a mandrel packer assembly designated generally by the numeral 62. While this assembly may be of various suitable constructions, it is particularly advantageous to provide a central annular member 64 slidable upon the exterior of the mandrel section 30, there being provided respectively upwardly and downwardly directed cup-shaped resilient packer members 66 and 68. The dual cups or packer members 66 and 68 automatically seal against the well casing 12 in response to whatever pressure differentials may be encountered above or below the packer assembly 62. The upwardly facing cup-shaped packer member 66 and the downwardly directed cupshaped packer element 68 may be of identical construction but reversely positioned and respectively function to prevent the passage downwardly or upwardly of fluid in the wall casing past the packer, when the latter is in place. The upper cup-shaped packer member 66 has an internal shoulder engaged by the lower end of the spacer sleeve cap neck 60 for a purpose to be subsequently set forth. as shown at 70.

Suitable sealing means such as O-rings or the like 72 are provided between the exterior surface of the mandrel lower section 30 and the adjacent internal surfaces, slidably engaged therewith, of the upper and lower packer members 66 and 68 and a by-pass port sleeve 74. This latter element has its upper end abutted against an annular internal shoulder 76 provided upon the lower cup-shaped packer member 68 while the lower end of the by-pass port sleeve is engaged by the previously mentioned safely release nut 36. A by-pass port 78 is provided in the upper end of the by-pass port sleeve 74 in the space between the lower mandrel section or sleeve 30 and the lower cup-shaped packer member 68, this by-pass port thus communicating with the well bore.

The function of the by-pass sleeve will now be understood from a comparison of FIGURE 2 which shows the sleeve in its initial by-pass port closing position and FIG- URE 4 which shows the sleeve in its by-pass port open position which is achieved by freeing of the safety release nut 36 from its threaded engagement at 34 with the lower mandrel sleeve 30. When this safety nut is released, and the mandrel is moved upwardly relative to the mandrel packer assembly the sleeve 74 which abuts against the shoulder 76 of the packer mandrel assembly 62 is moved downwardly upon the mandrel lower section until it abuts against the top surface of the retainer nut or cap 42 of the by-pass valve assembly 46. As seen in FIGURE 4, when this position is attained, the ports 32 in the mandrel lower section and 78 in the sleeve 74 are brought into registration thus establishing free communication between the interior of the well bore and the interior of the mandrel assembly and the zone isolation packer assembly 10.

It is to be understood that upon setting of the tension packer 14, the entire mandrel assembly 30, 22 extending throughout the length of the tool, together with spacer sleeves 50, 60 and 74 and the packer assembly 62 move as a unit with the tubing 18. However, when it is impossible to release the tension packer 14 to pull the entire tool upward in the well casing, or whenever it is desired to open the by-pass ports by matching ports 32 and 78 as shown in FIGURE 4 in order to release pressure below or to unload the tubing string 18 of fluid, the safety release nut 36 is disengaged. The safety release nut 36 may be released by drawing the pipe string 18 upwardly relative to the packers 14 and 62 to compress the safety release nut 36 against the member 74, which is prevented from moving upwardly by the mandrel packer 62, thereby shearing or stripping the threads from the safety release nut 36 thus allowing the safety release nut 36 and the members 74, 68, 64, 66, 60 and 50 which are slidably supported on the integrally joined mandrels 22 and 30 to slide downwardly into abutting relationship with the bypass valve assembly 46 thereby releasing the slips of the packer 14, and aligning the by-pass valve ports 32 and '78. Thereupon, the mandrel assembly 30, 22 can be moved upward with the tubing string 18, sliding independently of and within the spacer sleeves 50, 60 and 74 and the packer assembly 62 until the latter reach the lower end of the mandrel assembly as shown in FIGURE 4.

The disengagement of the safety release nut 36 from the lower mandrel sleeve may be effected in various ways. One advantageous manner consists in forming the threads of the nut 36 of a readily shearable material so that by merely applying enough pull upon the device through the pipe string or tubing 18, with the packer assembly 62 firmly in place in the well casing 12, these threads will be sheared and the continued upward travel of the mandrel assembly and the tool with respect to the packer assembly 62 will effect the relative downward travel of the by-pass sleeve 74 from its initial inoperative position in FIGURE 2 to its final and operative position opening the by-pass ports as shown in FIGURE 4.

Means are provided to prevent relative rotation between the by-pass port sleeve 74 and the lower mandrel section 30 and to maintain these elements in a guided rectilinearly traveling relation. For this purpose, as shown best in FIGURE 9, radially inwardly directed guide pin 80 is secured to the lower or other convenient portion of the by-pass port sleeve 74 and projects into a vertically elongated guide slot or channel 82 provided in the exterior surface of the mandrel lower sleeve 30. The member 80 thus serves to prevent relative rotation between the by-pass port sleeve and the mandrel lower section and further by abutting engagement with the upper and lower ends of the guide slot 82 will limit the extent of relative vertical rectilinear movement between these elements.

Attention is next directed more specifically to FIGURES 2, 8 and 11 for an understanding of the construction and operation of the by-pass valve assembly 46. The lower end of the lower mandrel section 30 constitutes a cylindrical barrel or bore in which is slidably received the cylindrical upper portion 84 of the piston 48, the latter having a diametrically reduced cylindrical lower portion or stem 86 which is slidably received in the cylindrical barrel formed by the interior of the retainer cap neck 44. As will be now apparent, the annular shoulder 88 which constitutes the junction of the portions 84 and 86 of the piston 48 is adapted to abut against the annular seat or shoulder 90 in the interior of the member 42 to act as a stop and prevent further downward travel of the piston in the by-pass valve assembly 46. Normally, the piston will be retained in a raised positon, shown in FIGURE 2 by means of a shear pin 92 extending diametrically through the neck 44 and the piston lower portion 86. However, when the pin 92 is sheared and the piston 48 forced downwardly by the application of hydraulic pressure thereto through the pipeline 18 and the passage 6 means through the zone isolation packer assembly 10, the piston will be retained in its downward position by the engagement of a locking ring 94 which is normally retained in an internal annular groove 96 within the neck 44 and which is resiliently engageable in the annular external locking groove 98 upon the exterior of the piston lower portion 86 when these grooves register as shown in FIG- URE 8. In this position, the piston is retained in its lower position until the device is withdrawn from the well bore and the engagement of the locking ring with the locking grooves is released in any suitable manner.

It will be further observed that the upper diametrically enlarged cylindrical portion 84 of the piston is provided with a cylindrical axial bore 100 therein which at its upper end is provided with a valve seat 102 and which adjacent its closed bottom end is provided with a plurality of by-pass inlet ports 104. A plurality of sealing rings such as O-rings 106 are provided at appropriate locations along the length of the exterior surface of the upper piston portion 84 and cooperate with the cylindrical wall of the interior of the lower mandrel section to establish a fluidtight seal therebetween. Obviously, a reverse arrangement could be employed with the sealing rings received in grooves in the internal surface of the mandrel lower section.

The upper end of the piston upper portion 84 is provided with a valve cage or closure dome 108 apertured as at 110 to loosely confine therein a non-return ball check valve 112 which thus cooperates with the valve seat 102. If desired, the valve cage or dome 108 may be either integral with or detachably connected to the upper portion of the piston, it being shown as integral for convenience of illustration only.

With the structure and the arrangement of the parts as hereinbefore described, the operation of the device is as follows. The parts are assembled into the position shown in FIGURE 2 upon the surface of the ground in readiness for the trip into the well bore. In this position, it will be noted that the packer assembly 62 which is slidably mounted upon the mandrel lower section 30 is retained in relatively fixed position through its engagement by the spacer sleeve 50 at its upper end and the by-pass valve sleeve 74 which in turn is held by the safety release nut 36. In this position the by-pass port 78 of the by-pass port sleeve 74 is held out of registration with the mandrel by-pass port or ports 32, so that these ports do not establish communication between the interior of the zone isolation packer assembly and the well bore. However, at this time the valve 48 is maintained in its upper position by the shear pin 92 and in this position the mandrel by-pass inlet port 38 is in registration with the valve by-pass inlet ports 104. Consequently, during movement of the tool through the well casing and the fluids therein, such fluids may freely flow through the registering ports 38 and 104, up through the Zone isolation packer assembly and through the pipe string or tubing 18 without hindrance. Consequently, passage of the device through the well casing does not produce any turbulence or swabbing action but encounters the minimum resistance and produces the minimum movement of the fluids in the well casing.

After the device has been lowered into the well bore to the desired position, the tension packer 14 is set in the conventional manner above the zone of interest and with the cupshaped packer assembly 62 being disposed below this zone. The packer 62 automatically seals in response to any differential pressure there across. Thus increased pressure between the tension packer 14 and the assembly 62 will seal the upper cup 66 against the casing and isolate the pressure throughout the desired interval. Alternatively, a pressure increase below the tool will seal the lower cup 68 against the casing, preventing this pressure from interference with the zone of interest between the packers 14 and 62.

The device is now in readiness for isolating the selected zone of a formation penetrated by the cased well bore. It will be understood that the well casing has been previously perforated at this desired zone in order to permit the desired treatment of that zone whether for testing or other purposes. With the zone of interest isolated by setting the tension packer above and by the cup-shaped packer 62 below, hydraulic fluid pressure is supplied from any suitable source to the interior of the pipe string 18, the zone isolation packer assembly 10 and to the check valve 112 and the piston 48. This hydraulic fluid is retained in the Well bore since it is confined between the tension packer 14 and the mandrel packer assembly 62. The pressure thus applied will shear the pin 92 and force the piston 48 downwardly in the by-pass valve assembly barrel until the shoulders 88 and 90 of the piston and of the cap 42 abut each other as shown in FIGURE 8. In this position the by-pass ports 38 in the lower mandrel section and 104 in the piston are moved out of registration from the by-pass opening position of FIGURE 2 to the by-pass closing position of FIGURE 8. Consequently, both the upper set of by-pass ports 32 and 78 are closed in the manner shown in FIGURE 2 and the lower set of ports 38 and 104 are closed as shown in FIG- URE 8. The device is now in readiness for treating the formation. Any suitable treating agent such as a fracturing agent, an acidizing agent or the like is now applied through the pipe string 18 and into the mandrel assembly, and from thence passes by means of the apertures 24 in the upper mandrel section 22 into the annular space between that section and the spacer sleeve 50, emerging from the latter through the ports 54 into the isolated zone between the two packers 14 and 62 to thus treat the zone. As previously mentioned, this treating operation may consist of withdrawing fluids from the isolated zone for testing purposes and the like.

After the treating operation has been completed, the tension packer 14 is released, in order that the tool may be shifted upwardly or withdrawn from the Well casing. An upward pull is now applied to the pipe string 18 which in turn pulls the mandrel assembly upwardly. If the tension packer cannot be released the upward pull applies a force to the threads of the safety release nut 36 as the latter is forced against the lower end of the by-pass sleeve 74 so that these threads are sheared and the nut 36 is now free to drop down the lower mandrel section until it rests upon the cap 42, this position being shown in FIGURE 4. Further upward pull on the pipe string 18 and the zone isolation packer assembly 10 now causes the mandrel assembly to slide through. spacer sleeves 50, 60 and the packer assembly 62, thereby causing a relative downward travel of the by-pass port sleeve 74 upon the lower mandrel assembly until this sleeve abuts against the nut 36 and the latter in turn abuts against the cap 42. At this time, the by-pass ports 32 in the lower mandrel section 30 are aligned with the by-pass ports 78 of the by-pass sleeve 74 thus establishing communication for well fluids from the interior of the well bore into the interior of the device. Consequently, further upward travel will move the tool upwardly in the well bore with a minimum disturbance of the well fluids therein as set forth in connection with the discussion of the operation of the other set of by-pass ports. When the tool reaches the surface, it is merely necessary to disengage the lock Lr ring 94 which retained the piston 48 in its lowered position after rupture of the shear pin 92 and then again shift the packer assembly 62 and the associated spacer sleeve 50 and the by-pass valve sleeve 74 and to apply a new safety retaining nut 36 to thus hold the parts in their assembled position ready for the next operation.

It is to be noted that in some instances it may be desirable to treat one or more vertically spaced zones. This can be effected with this tool after the first or lowermost isolated zone has been treated by releasing the tension packer 14, and then moving the entire device upwardly in the well bore to the desired new location. If the tension packer cannot be released, it is then necessary to disengage the safety release nut 36 as above mentioned and pull the tubing string and the tool.

It will be appreciated that the lengths of the mandrel sections, spacer and by-pass port sleeves will be appropriately selected to correspond with the size of the zone to be isolated.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A zone isolating and treating device for wells comprising first and second spaced packers each releasably seatable in a well bore and defining therebetween an isolated region having free and continuous communication with an adjacent surrounding zone of the well which is to be isolated and treated, a hollow mandrel upon which said packers are mounted, said second packer being mounted for relative sliding movement toward and away from said first packer, releasable means preventing said sliding movement of said second packer, passage means establishing communication of the mandrel interior with said isolated region for treating the communicating zone, a first and a second by-pass means connecting the mandrel interior with the well bore below said packers and isolated region, a pair of control means each associated with said mandrel and each controlling one of said by-pass means and selectively operable to effect opening of the associated by-pass means when the other by-pass means is closed.

2. The combination of claim 1 wherein one of said packers includes oppositely divergent cup-shaped packer members mounted upon said mandrel and radially expansible into sealing engagement with the well bore when subjected to a pressure differential upon the opposite sides of said one packer.

References Cited by the Examiner UNITED STATES PATENTS 2,156,709 5/1939 Taylor 166-127 2,244,354 6/1941 Boggs et a1. 166146 2,426,164 8/1947 Brukelman 166-146 2,716,456 8/1955 Brown 166-27 2,738,013 3/1956 Lynes 166l47 BENJAMIN HERSH, Primany Examiner. 

1. A ZONE ISOLATING AND TREATING DEVICE FOR WELLS COMPRISING FIRST AND SECOND SPACED PACKERS EACH RELEASABLY SEATABLE IN A WELL BORE AND DEFINING THEREBETWEEN AN ISOLATED REGION HAVING FREE AND CONTINUOUS COMMUNICATIONS WITH AN ADJACENT SURROUNDING ZONE OF THE WELL WHICH IS TO BE ISOLATED AND TREATED, A HOLLOW MANDREL UPON WHICH SAID PACKERS ARE MOUNTED, SAID SECOND PACKER BEING MOUNTED FOR RELATIVE SLIDING MOVEMENT TOWARD AND AWAY FROM SAID FIRST PACKER, RELEASABLE MEANS PREVENTING SAID SLIDING MOVEMENT OF SAID SECOND PACKER, PASSAGE MEANS ESTABLISHING COMMUNICATION OF THE MANDREL INTERIOR WITH SAID ISOLATED REGION FOR TREATING THE COMMUNICATING ZONE, A FIRST AND A SECOND BY-PASS MEANS CONNECTING THE MANDREL INTERIOR WITH THE WELL BORE BELOW SAID PACKERS AND ISOLATED REGION, A PAIR OF CONTROL MEANS EACH ASSOCAITED WITH SAID MANDREL AND EACH CONTROLLING ONE OF SAID BY-PASS MEANS AND SELECTIVELY OPERABLE TO EFFECT OPENIGN OF THE ASSOCIATED BY-PASS MEANS WHEN THE OTHER BY-PASS MEANS IS CLOSED. 